I have a look up field which drops down when clicked. 

The drop down shows me data from another field (i'll call it the 2nd field) in the related table.

The look up field varies in length with a maximum 10 characters.

I use "courier" font thanks to some suggestions on here as to how to get the data aligned.

The issue is that because the look up filed varies in the number of characters I cannot get the data from the 2nd field to align in the drop down list.

The beginning of the solution is for me to use the "length" function to find out how many chracters are actually in the look up field. 

I then deduct the number of characters from the 10 maximum and this gives me the number of additional characters I need to add in order for the 2nd field to appear aligned in the drop down list.

So, what I need to do is to work out a way of adding spaces: i see it this way - if the primary look up field is 4 characters then I need to add 6 spaces at the front of the 2nd field to make it align.

The issue is how do I write the calculation to add the spaces?

I don't understand many of your words ( FileMaker terms ), but to obtain a text with some spaces in front you could use:

 

Right ( "          " & yourField ; 10 ) // between quotes there are 10 spaces

Thanks - I'll give that a go